1. Field of the Invention
The present invention relates to a thermoelectric conversion module and a method for manufacturing the thermoelectric conversion module.
2. Description of the Related Art
In recent years, thermoelectric conversion techniques for converting heat to electricity have been advanced. Particularly, in recent years, for the purpose of preventing global warming, the reduction in carbon dioxide has become a critical issue, and thermoelectric conversion modules that are able to convert heat directly to electricity have been attracting attention as one of the effective waste heat recovery techniques.
One of such thermoelectric conversion modules is configured to have multiple thermoelectric conversion element sections laminated with an insulating layer interposed therebetween, in which a plurality of n-type thermoelectric conversion material layers and a plurality of p-type thermoelectric conversion material layers are provided in a serpentine shape (zigzag shape) so that multiple p-n junctions are arranged in series, achieving that the sum of thermal electromotive forces generated in the respective p-n junctions can be extracted (see FIGS. 1 and 2 of Japanese Unexamined Patent Publication No. 11-177154)
Such a thermoelectric module is manufactured by, for example, a method as described below.
First, as shown in FIGS. 8A and 8B, a thermoelectric component sheet 55 is prepared and includes p-type thermoelectric conversion material layers (patterns) 52 and n-type thermoelectric conversion material layers (patterns) 53 formed by printing each of a Ni paste for the formation of n-type thermoelectric conversion material layers and a Cu paste for the formation of p-type thermoelectric conversion material layers to have a predetermined width (for example, 150 μm) and a printed width (for example, 20 μm) on the principal surface of a insulator green sheet 51 with a predetermined thickness (for example, 50 μm).
Then, the thermoelectric component sheet 55 is laminated as shown in FIG. 9, followed by pressure bonding, and an uncalcined laminated body 54a obtained is calcined.
This method provides a calcined laminated body 54 (FIG. 10) which has a structure obtained by laminating the multiple thermoelectric components 55 each provided with a thermoelectric conversion element section 58 composed of p-type thermoelectric conversion material layers 52 and n-type thermoelectric conversion material layers 53 connected in series with the insulating layer 51 interposed therebetween.
Then, as shown in FIG. 10, external electrodes 57a, 57b are formed on the calcined laminated body 54 so as to provide conduction to the thermoelectric conversion element sections 58 (FIGS. 8A and 8B).
The thus obtained thermoelectric conversion module 60 (FIG. 10) is provided and used in a mode, for example, with an edge surface 56a side as a higher temperature side and an edge surface 56b side as a lower temperature side, perpendicular to the principal surface of the insulating layer obtained by the calcination of the insulator green sheet 51 described above.
Meanwhile, in the thermoelectric conversion module 60 configured as described above, it is necessary to increase the occupancy of the thermoelectric conversion materials in the thermoelectric conversion module (the ratio of the area occupied by the thermoelectric conversion materials in a plane perpendicular to the direction of a temperature difference caused in the thermoelectric conversion module) in order to increase the output per unit area of the module (plane area of the product). For that purpose, it is necessary to increase the thicknesses of the p-type and n-type thermoelectric conversion materials in relation to the thickness of the insulating layer.
However, as in Japanese Unexamined Patent Publication No. 11-177154 described above, in the case of the method of laminating, on an insulator green sheet, sheets with p-type thermoelectric conversion material patterns and n-type thermoelectric conversion material patterns formed, increase in thickness the p-type thermoelectric conversion material patterns and n-type thermoelectric conversion material patterns is likely to cause deviation of the lamination and deformation in the step of laminating or pressure bonding. In particular, when the p-type thermoelectric conversion material patterns and n-type thermoelectric conversion material patterns are increased in thickness more than the insulator green sheet, deviation of the lamination and deformation are easily caused, and in fact, it is the case that it is not possible to increase the thicknesses of the thermoelectric conversion material layers more than the thickness of the insulating layer.